|
|
Ken,
I am not certain that the best places for
air entrance and exit on an airplane change much with speed. You need
entrances in high pressure areas and exits in low pressure areas. The top
of the cowl is a high pressure area and if you try to exit air there, I suspect
that it will partially block the flow.
While I have heard a lot of good stuff
about the Paul Lamar book, I usually try to get my guidance from folks who have
actually built an airplane.
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Kenneth Johnson
Sent: Wednesday, October 31, 2012
11:03 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: flow path
in conventional radiator
Sorry to get back to you so late, but am
now just getting caught up on emails. When I have free time, I am usually
out in my garage working on the plane. If you have not read "How to
Cool Your Wankel" by Paul Lamar, I would recommend it. It would be
worth your time.
The suggestion to flow air from the bottom
up was not made by Paul, but was my thoughts regarding the airplane I am
building. The Zenith 801 is the four passenger high wing STOL bush-type
plane. It's top speed is 110 MPH. It's primary purpose is getting
in and out of short, grass strips. Where engine cooling is most needed is
on short runway take-off with high obstacles such as trees at the runway's
end. Stall speed is about 40 MPH. This just means there is very
little air flowing through the cooling system on take-off. The
airplane is at a high angle of attack until obstacles are cleared. And
again, at this high angle of attack, cooling flow is different and airspeed is
slow.
Having the cowl opening on the bottom front
of the cowl where air flows directly through the radiators and having outlets
on the top sides of the cowl would allow air to flow best when it is most
needed to cool the engine. At flat and level flying, the air would still
flow, but the higher speed would provide more cooling.
What makes this plane unique is it is not
an RV where one is flying at 170 knots and has a mile long
runway.
Please read Paul's book and give me your
thoughts. Thanks for your comments.
From: Tracy
<rwstracy@gmail.com>
To: Rotary
motors in aircraft <flyrotary@lancaironline.net>
Sent: Wednesday, October 24, 2012
12:21 PM
Subject: [FlyRotary] Re: flow path
in conventional radiator
On Oct 24, 2012, at 10:14 AM, Kenneth Johnson <kjohnsondds@yahoo.com>
wrote:
> A more efficient design would have intake air entering the bottom
anterior of the the cowl and to pass through the radiator. As this air is
heated by the radiator it rises and should exit the top sides of the
cowl. No one has done that because of the risk of engine oil on the
windshield.
I haven't read Paul's book but if this is an example of his suggestions, I
wouldn't have much confidence in it.
Two basic rules of thumb for A/C cooling systems are:
1. Turning high speed air is hard to do and loss prone energy wise.
2. The pressure represented by convection of rising hot air is not
significant and can safely be ignored for our purposes.
Tracy
--
Homepage: http://www.flyrotary.com/
Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html
|
|